We are playing our GD 1938 scenario. In this scenario, China, GB and France has diplomatic blocks in the USA turn (to prevent USA from attacking them). However, the USA, once activated, can offer alliance to these countries by event cards (alliance offer is unilateral and automatically accepted). The alliance cards simply change relationship with target regime, nothing more, so I noticed the following effects

1-USA launches card alliance with GB. It creates an alliance between USA, France, GB, USSR and brings USA to war vs. Germany and Italy 2-In the following round I noticed the USA was still at war with Germany and Italy, but there were no more alliance with France and USSR. So I used card alliance with France. While it worked, it changed relation with Germany and Italy to peace (????). No troubles....I declared war again 3-When I played the alliance with China card (just for experience, I didn´t do it in the game), the USA became a China allied, but it didn´t enter war against Japan, althought China is at war with Japan